This study aims to develop the concept of renin profiling in children and adolescents primarily with hypertension. Results obtained in hypertensive children are currently being compared to values developed in normal volunteers. The renin response to acute volume contraction and three days of a low salt diet is currently under investigation. Simultaneously the incidence of hyperuricemia and its mechanism are being evaluated. To date, uric acid metabolism has been evaluated in approximately 50 hypertensive children. Thirty to forty percent have had uric acid abnormalities. Also, it has been shown that the presence of hyperuricemia alters the renal response to the oral administration of a diuretic. The data developed in some of these children are also being added to data already available in these children who have participated in one of the National Heart, Lung & Blood Institute's studies entitled "Antecedents of Adolescent Hypertension."